Wireless telecommunications networks require significant effort in placing nodes or access points within a geographic area to ensure proper wireless coverage for users in that area. An access point (AP) is typically a physical edge device that allows wireless user devices to access network resources, and it is sometimes referred to as a node. With cellular telephone networks, service providers establishing base stations or APs must contend with topographical or terrain constraints, buildings, foliage, and other obstructions that attenuate or block wireless transmissions.
Similar problems occur when establishing a wireless local area network (WLAN). WANs typically employ existing protocols such as those under IEEE 802.11, which is a specification that defines WLAN data link and physical layers. The 802.11 specification includes a media access control (MAC) sublayer within a data link layer, and two sublayers of the physical layer (PHY), orthogonal frequency division multiplexing (OFDM) and a direct-sequence spread-spectrum (DSSS) modulation scheme. The Bluetooth specification (IEEE 802.15) uses a frequency-hopping spread spectrum (FHSS) modulation scheme.
The FHSS technique modulates a data signal with a narrow band carrier signal that “hops” in a predictable sequence from frequency to frequency as a function of time over a wide band of frequencies. Interference is reduced because a narrow band interferer affects the spread-spectrum signal only if both are transmitting at the same frequency at the same time. The transmission frequencies are determined by a spreading (hopping) code. The receiver must be set to the same hopping code and must listen for the incoming signal at the proper time and frequency to receive the signal. OFDM splits a wide frequency band into a number of narrow frequency bands and sends data across the sub-channels. DSSS combines a data signal at the sending station with a higher data rate bit sequence that often is referred to as a “chip sequence.” A high processing gain increases the signal's resistance to interference.
Various IEEE 802.11 protocols exist, including 802.11a, 802.11b, 802.11g, 802.11e, 802.11i and others. These and other protocols are often referred to as “WiFi,” which is short for wireless fidelity. Other short-range wireless protocols include Bluetooth (IEEE 802.15), and Hiperlan, which has been adopted by the European Telecommunications Standards Institute (ETSI).
With increasing demands on quality of service, including user coverage, data throughput, RF interference, etc., planning an optimization of wireless networks has become an ever more important issue. While OFDM and DSSS help to reduce interference, they of course suffer from obstacles within their wireless range that attenuate their signals. Further, each has limited range, and thus multiple access points under any of the 802.11 protocols must be placed within a large area to ensure proper coverage. These are only some of the concerns faced in establishing a WLAN.
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.
In the drawings, the same reference numbers and acronyms identify elements or acts with the same or similar functionality for ease of understanding and convenience. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 1104 is first introduced and discussed with respect to FIG. 11).
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